Electric coolant pump and manufacturing method for movable unit of the same

Abstract

An electric coolant pump includes a pump house, a motor connected to the pump house, and an impeller housed in the pump house and driven by the motor. The motor includes a stator and a movable unit rotatably mounted within the stator. The stator is provided with a central shaft. The movable unit includes a support body, a bearing assembly fixedly embedded in the support body, a rotor core fixed to the support body, and a plurality of permanent magnets attached to the rotor core. The bearing assembly includes at least one bearing rotatably sleeved on the central shaft. The support body is formed by an injection-molding process to wrap the bearing assembly and fixed connecting bearing assembly and the rotor core.

The invention claimed is: 
     
       1. An electric coolant pump, comprising
 a pump house; 
 a motor connected to the pump house and comprising:
 a stator with a fixed central shaft; and 
 a movable unit rotatably mounted within the stator, the movable unit comprising a support body, a bearing assembly connected to the support body, a rotor core fixed to the support body and a plurality of permanent magnets attached to the rotor core, the bearing assembly comprising a cylindrical positioning sleeve and two bearings positioned at opposite ends of the positioning sleeve, the positioning sleeve and the bearings are sleeved on the central shaft, the positioning sleeve is in clearance fit with the central shaft, the two bearings rotatably supported on the central shaft, wherein the support body is formed by an injection-molding process to wrap the bearing assembly and fixedly connecting bearing assembly and the rotor core, the bearings are fixedly connected to the positioning sleeve through the support body being directly overmolded by the injection-molding process on both the bearings and the positioning sleeve; 
 
 an impeller housed in the pump house and driven by the motor. 
 
     
     
       2. The electric coolant pump of  claim 1 , wherein opposite axial ends of the positioning sleeve respectively defines a positioning groove, the two bearings are respectively embedded in the positioning grooves of the positioning sleeve. 
     
     
       3. The electric coolant pump of  claim 1 , wherein one of the bearings is fixed to the impeller and the other one bearing is fixed to an end of the support body away from the impeller. 
     
     
       4. The electric coolant pump of  claim 1 , wherein an inner diameter of the positioning sleeve is larger than that of the bearings. 
     
     
       5. The electric coolant pump of  claim 1 , wherein at least part of the impeller is integrally formed with the support body by the injection-molding process. 
     
     
       6. The electric coolant pump of  claim 5 , wherein the impeller comprises a bottom bezel, a cover bezel opposite and spaced apart from the bottom bezel, and a plurality of vanes connected between the bottom bezel and the cover bezel, the plurality of vanes is integrally formed with the bottom bezel. 
     
     
       7. The electric coolant pump of  claim 1 , wherein the support body is provided with a first annular ring and a second annular ring axially spaced from and substantially parallel to each other, the rotor core is sandwiched between the first and second annular rings, the rotor core are wrapped with a protective sleeve, the protective sleeve mates with the support body to cover all of the outer and inner surfaces of the rotor core. 
     
     
       8. The electric coolant pump of  claim 1 , wherein a plurality of recesses is defined in an outer surface of each of the bearings, the support body forms a plurality of bosses correspondingly snapped into the recesses. 
     
     
       9. The electric coolant pump of  claim 1 , wherein the stator further comprises a cylindrical stator outer casing, a stator inner casing, a stator core disposed between the stator outer casing and the stator inner casing, a stator winding wound around the stator core, the movable unit is housed in the stator inner casing, an end of the stator outer casing and an end of the stator inner casing are fixed to the pump house. 
     
     
       10. The electric coolant pump of  claim 9 , wherein the stator inner casing comprises a cylindrical portion opened at one of opposite axial ends and closed at the other end with a bottom plate, and an annular flange surrounding the open end of the cylindrical portion, the annular flange is fastened to the pump house, an inner cavity of the cylindrical portion is in communication with a pump chamber of the pump house. 
     
     
       11. The electric coolant pump of  claim 10 , wherein one of opposite ends of the central shaft is fixed to the bottom plate of the cylindrical portion, and the other end of the central shaft is fixed to the pump house through the impeller. 
     
     
       12. The electric coolant pump of  claim 1 , wherein each of the two bearings is a bushing made of graphite or a material having a low coefficient of friction, and is in friction fit with the central shaft. 
     
     
       13. A manufacturing method for the movable unit of the electric coolant pump of  claim 1 , comprising:
 integrating the rotor core and the permanent magnets, comprising inserting the permanent magnets into the rotor core, and then forming a protective sleeve wrapping the rotor core by a process of insert-molding; 
 preparing the bearing assembly by providing the positioning sleeve and two bearings positioned at opposite ends of the positioning sleeve; and 
 forming the support body, and integrating the pre-integrated permanent magnets and rotor core, and the bearing assembly, comprising positioning the pre-integrated permanent magnets and rotor core, and the bearing assembly in an injection tooling, with the bearing assembly sleeved by the rotor core, and then injecting a resin material into the injection tooling to form the support body fixedly connecting the pre-integrated permanent magnets and rotor core, the bearings and the positioning sleeve by the injection-molding process. 
 
     
     
       14. The manufacturing method of  claim 13 , wherein in forming the support body by the injection-molding process, a gap between an outer circumferential wall of the bearing assembly and an inner wall of the rotor core is filled with the resin material. 
     
     
       15. The manufacturing method of  claim 13 , preparing the bearing assembly comprises respectively embedding the two bearings at two positioning grooves respectively defined in two opposite ends of the positioning sleeve to axially aligned the two bearings and the positioning sleeve.